Arthritis in rats after systemic injection of streptococcal cells or cell walls

Models for T-large granular lymphocytic leukemia: how to mimic the cellular interplays in malignant autoimmunity

T-large granular lymphocytic leukemia (T-LGLL) is a chronic lymphoproliferative disorder characterized by clonal expansions of cytotoxic T-cells. It presents with cytopenias that are not explained by the typically low leukemic burden. Notably, T-LGLL is frequently accompanied by autoimmune disorders, particularly rheumatoid arthritis (RA). As clonal T-cell expansions are also increasingly identified in autoimmune-driven conditions, better models of T-LGLL's pathogenesis as a spectrum of (auto)antigen-driven oligoclonal hierarchies towards overt leukemic escape with associated immune dysregulations would provide details to a valuable prototype for determinants of T-cell fitness and transformation as well as T-cell instructed dysfunctions of other immune cells. Such insights would advance our concepts of cancer biology and immunology. Common molecular links between T-LGLL and autoimmune diseases include activation of JAK/STAT signaling, proinflammatory cytokine environments, and antigen-driven immune responses. Current murine models address these mechanisms rather individually: JAK/STAT based systems replicate pathway activation, cytokine-driven models simulate inflammatory conditions, and RA models often mimic antigen stimulation. However, none of these fully captures the duality of clonal T-cell expansion and the complex immune dysregulations, inherent to T-LGLL. This review examines criteria for autochthonous in-vivo T-LGLL models and evaluates existing systems, identifying their strengths, limitations, and specific representations of clinico-pathologic aspects of LGLL. Prominent transgenic models, for example, not only manipulate the T-cell compartment but also indiscriminately alter the tumor microenvironment, impeding research on the specific role of elements of the LGLL micromilieu. We propose strategies to overcome such insufficiencies of present models. Overall, our critical appraisal emphasizes the need for novel comprehensive models that more faithfully integrate the key features of T-LGLL or for models that, by featuring specific pathogenetic aspects of the disease, would supplement existing incomplete systems. We expect such new model systems to aid in better understanding the cancer-immunity interface and in assessing novel therapeutic approaches for T-LGLL.

Proteasome Inhibitors: Potential in Rheumatoid Arthritis Therapy?

Rheumatoid arthritis (RA) is a chronic autoimmune disease that leads to the destruction of peripheral joint cartilage and bone tissue. Despite the advent of biological therapies in the past decades, the complete remission of RA patients is still out of reach. Therefore, the search for novel therapeutic approaches is still open in the field of RA. Proteasome inhibitors (PIs) were originally designed to be used in hematological malignancies like multiple myeloma. However, evidence has shown that they are potent inhibitors of the NF-κB pathway, which plays a pivotal role in inflammatory processes and RA. Furthermore, inhibition of cell activation and induction of apoptosis was also reported about PIs. In the present review, we summarize the current knowledge about the potential effects of PIs in RA based on reports from animal and human studies. We believe that there is substantial potential in the use of PIs in RA therapy either alone or in combination with the medications already used.

Bacterial and host enzymes modulate the inflammatory response produced by the peptidoglycan of the Lyme disease agent

The spirochete Borrelia burgdorferi causes Lyme disease. In some patients, an excessive, dysregulated proinflammatory immune response can develop in joints leading to persistent arthritis. In such patients, persistence of antigenic B. burgdorferi peptidoglycan (PGBb) fragments within joint tissues may contribute to the immunopathogenesis, even after appropriate antibiotic treatment. In live B. burgdorferi cells, the outer membrane shields the polymeric PGBb sacculus from exposure to the immune system. However, unlike most diderm bacteria, B. burgdorferi releases PGBb turnover products into its environment due to the absence of recycling activity. In this study, we identified the released PGBb fragments using a mass spectrometry-based approach. By characterizing the l,d-carboxypeptidase activity of B. burgdorferi protein BB0605 (renamed DacA), we found that PGBb turnover largely occurs at sites of PGBb synthesis. In parallel, we demonstrated that the lytic transglycosylase activity associated with BB0259 (renamed MltS) releases PGBb fragments with 1,6-anhydro bond on their N-acetylmuramyl residues. Stimulation of human cell lines with various synthetic PGBb fragments revealed that 1,6-anhydromuramyl-containing PGBb fragments are poor inducers of a NOD2-dependent immune response relative to their hydrated counterparts. We also showed that the activity of the human N-acetylmuramyl-l-alanine amidase PGLYRP2, which reduces the immunogenicity of PGBb material, is low in joint (synovial) fluids relative to serum. Altogether, our findings suggest that MltS activity helps B. burgdorferi evade PG-based immune detection by NOD2 during growth despite shedding PGBb fragments and that PGBb-induced immunopathology likely results from host sensing of PGBb material from dead (lysed) spirochetes. Additionally, our results suggest the possibility that natural variation in PGLYRP2 activity may contribute to differences in susceptibility to PG-induced inflammation across tissues and individuals.

An update of murine models and their methodologies in immune-mediated joint damage and pain research

Murine models have played an indispensable role in the understanding of rheumatic and musculoskeletal disorders (RMD), elucidating the genetic, endocrine and biomechanical pathways involved in joint pathology and associated pain. To date, the available models in RMD can be classified as induced or spontaneous, both incorporating transgenic alternatives that improve specific insights. It is worth noting that the selection of the most appropriate model together with the evaluation of their specific characteristics and technical capabilities are crucial when designing the experiments. Furthermore, it is also imperative to consistently adhere to the ethical standards concerning animal experimentation. Recognizing the inherent limitation that any model can entirely encapsulates the complexity of the pathophysiology of these conditions, the aim of this review is to provide an updated overview on the methodology of current murine models in major arthropathies and their immune-mediated pathways, addressing to basic, translational and pharmacological research in joint damage and pain.

The Bowel-Associated Arthritis-Dermatosis Syndrome (BADAS): A Systematic Review

Bowel-associated arthritis-dermatosis syndrome (BADAS) is a rare neutrophilic dermatosis that was first described in 1971 in patients who underwent bypass surgery for obesity. Over the years, the number of reported cases associated with medical gastroenterological conditions, particularly inflammatory bowel disease (IBD), has progressively increased. To date, there are no systematic reviews in the literature on BADAS. The design of an a priori protocol was based on PRISMA guidelines, and a search of PubMed and Scopus databases was conducted for articles published between 1971 and 2023 related to the topic. Fifty-one articles including 113 patients with BADAS were analyzed in this systematic review. Bariatric surgery and IBD were the most frequently reported causes of BADAS, accounting for 63.7% and 24.7% of all cases, respectively. A total of 85% of cases displayed the typical dermatological presentation, including urticarial maculopapular lesions centered by a vesicopustule, with the majority of lesions located on the upper limbs (73.5%). Polyarthralgia or localized arthritis were always present. Atypical presentations included cellulitis-like, erythema-nodosum-like, Sweet-syndrome-like and pyoderma-gangrenosum-like manifestations. Gastrointestinal symptoms were frequently observed in IBD-related cases (67.9%). The histopathology showed a neutrophilic infiltrate (96.6%). The most commonly used treatment regimens consisted of systemic corticosteroids, metronidazole and tetracyclines, either alone or in combination. A relapsing-remitting course was observed in 52.1% of patients. In conclusion, BADAS is a neutrophilic dermatosis that presents with a wide variety of cutaneous manifestations, both typical and atypical. Gastrointestinal symptoms are frequently observed, particularly in cases related to IBD. The histopathology is clear but not specific compared with other neutrophilic dermatoses. The diagnosis can be challenging, but the relapsing-remitting course and the strong association with polyarthralgia and gastrointestinal disease can aid in the diagnosis.

Advances in experimental models of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by persistent articular inflammation and joint damage. RA was first described over 200 years ago; however, its etiology and pathophysiology remain insufficiently understood. The current treatment of RA is mainly empirical or based on the current understanding of etiology with limited efficacy and/or substantial side effects. Thus, the development of safer and more potent therapeutics, validated and optimized in experimental models, is urgently required. To improve the transition from bench to bedside, researchers must carefully select the appropriate experimental models as well as draw the right conclusions. Here, we summarize the establishment, pathological features, potential mechanisms, advantages, and limitations of the currently available RA models. The aim of the review is to help researchers better understand available RA models; discuss future trends in RA model development, which can help highlight new translational and human-based avenues in RA research.

Deciphering the pharmacological mechanisms of Chaenomeles Fructus against rheumatoid arthritis by integrating network pharmacology and experimental validation

Chaenomeles Fructus is a plant that can be used for both food and medicine. Modern studies have shown that Chaenomeles Fructus has anti-inflammatory and immunosuppressive effects on arthritis. However, the mechanism of action of Chaenomeles Fructus on rheumatoid arthritis (RA) and its main active ingredients are still unclear. This study was aimed at devising an integrated strategy for investigating the bioactivity constituents and possible pharmacological mechanisms of Chaenomeles Fructus against RA. The components of Chaenomeles Fructus were analyzed using UPLC-Q-Exactive orbitrap MS techniques and applied to screen the active components of Chaenomeles Fructus according to their oral bioavailability and drug-likeness index. Then, we speculated on the potential molecular mechanisms of Chaenomeles Fructus against RA through a network pharmacology analysis. Finally, the potential molecular mechanisms of Chaenomeles Fructus against RA were validated in a complete Freund's adjuvant (CFA)-induced RA rat model. We identified 48 components in Chaenomeles Fructus and screened seven bioactive ingredients. The results of the network pharmacology prediction and the experimental verification results were analyzed by Venn analysis, and the experimental results concluded that Chaenomeles Fructus mainly interferes with the inflammation of RA by inhibiting arachidonic acid metabolism and the MAPK signaling pathway. This study identified the ingredients of Chaenomeles Fructus by UPLC-Q-Exactive orbitrap MS and explained the possible mechanisms of Chaenomeles Fructus against RA by integrating network pharmacology and experimental validation.

Streptococcus agalactiae infection caused spinal deformity in juvenile red tilapia (Oreochromis sp.)

A case of juvenile red tilapia (Oreochromis sp.) showing body deformity due to spinal curvature was investigated. Approximately 20% of the crop (4,000 fish/crop) was affected. Bacterial isolation from the kidney and tissue surrounding the spinal lesion of the affected fish was negative. Histopathology revealed granulomatous inflammation and Gram-positive cocci in connective tissues around the bone and notochord. PCR assay confirmed the presence of S. agalactiae in the spinal tissue lesion. Spinal deformity in red tilapia observed in our study may be associated with the inflammatory process and granuloma that compress the skeleton structure. The present study highlights chronic streptococcosis in tilapia culture that may be unnoticed.

LC-MS/MS-Based Serum Protein Profiling for Identification of Candidate Biomarkers in Pakistani Rheumatoid Arthritis Patients

Rheumatoid arthritis is an autoimmune disorder of complex disease etiology. Currently available serological diagnostic markers lack in terms of sensitivity and specificity and thus additional biomarkers are warranted for early disease diagnosis and management. We aimed to screen and compare serum proteome profiles of rheumatoid arthritis serotypes with healthy controls in the Pakistani population for identification of potential disease biomarkers. Serum samples from rheumatoid arthritis patients and healthy controls were enriched for low abundance proteins using ProteoMinerTM columns. Rheumatoid arthritis patients were assigned to one of the four serotypes based on anti-citrullinated peptide antibodies and rheumatoid factor. Serum protein profiles were analyzed via liquid chromatography-tandem mass spectrometry. The changes in the protein abundances were determined using label-free quantification software ProgenesisQITM followed by pathway analysis. Findings were validated in an independent cohort of patients and healthy controls using an enzyme-linked immunosorbent assay. A total of 213 proteins were identified. Comparative analysis of all groups (false discovery rate < 0.05, >2-fold change, and identified with ≥2 unique peptides) identified ten proteins that were differentially expressed between rheumatoid arthritis serotypes and healthy controls including pregnancy zone protein, selenoprotein P, C4b-binding protein beta chain, apolipoprotein M, N-acetylmuramoyl-L-alanine amidase, catalytic chain, oncoprotein-induced transcript 3 protein, Carboxypeptidase N subunit 2, Apolipoprotein C-I and Apolipoprotein C-III. Pathway analysis predicted inhibition of liver X receptor/retinoid X receptor activation pathway and production of nitric oxide and reactive oxygen species pathway in macrophages in all serotypes. A catalogue of potential serum biomarkers for rheumatoid arthritis were identified. These biomarkers can be further evaluated in larger cohorts from different populations for their diagnostic and prognostic potential.

Mechanism by which immune complexes are deposited in hosts tissue

We offer an explanation how immune complexes are deposited in tissues of auto-immune disorders in humans. These disorders are characterized by the accumulation in tissues of large numbers of neutrophils, which can shed out long extracellular traps (NETs) rich in a nucleosome and in highly opsonic poly cations, histone, LL37, defensins and elastase possessing properties similar to antibodies. These can bind by strong electrostatic forces to negatively charged domains in immune globulins, thus facilitating their deposition and internalization by tissue cells. However, the main cause for tissue damage in auto-immune patients is inflicted by the plethora of toxic pro-inflammatory agents released by activated neutrophils. To ameliorate tissue damage and the cytokine storms, it is recommended to administer to patients highly anionic heparins accompanied by steroids, methotrexate, colchicine, copaxone, and also by additional agents which retarded neutrophil functions.

Association between Oncostatin M Expression and Inflammatory Phenotype in Experimental Arthritis Models and Osteoarthritis Patients

Pro-inflammatory cytokines are considered to play a major role in osteoarthritis (OA), yet so far, the specific cytokines involved in the pathology of OA have not been identified. Oncostatin M (OSM) is a cytokine from the interleukin 6 (IL-6) family that has been shown to be elevated in synovial fluid of most rheumatoid arthritis (RA) patients, but only in a limited subset of OA patients. Little is known about OSM in the different joint tissues during OA and how its expression correlates with hallmarks of disease. Here, we mapped OSM expression in the joint tissues of two rat models of arthritis: an acute inflammatory model and an instability-induced osteoarthritic model. OSM expression was correlated with hallmarks of OA, namely cartilage damage, synovitis, and osteophyte formation. Reanalysis of an existing dataset on cytokine profiling of OA synovial fluid was performed to assess pattern differences between patients positive and negative for OSM. In the inflammatory model, OSM expression correlated with synovitis and osteophyte formation but not with cartilage damage. On the contrary, in the instability model of OA, an increase in synovitis, cartilage damage, and osteophyte formation was observed without changes in OSM expression. In line with these findings, synovial fluid of OA patients with detectable OSM contained higher levels of other inflammatory cytokines, namely interferon gamma (IFN-γ), IL-1α and tumor necrosis factor alpha (TNF-α), likely indicating a more inflammatory state. Taken together these data indicate OSM might play a prominent role in inflammatory phenotypes of OA.

A novel aspect may explain the mechanisms of pathogenicity of rheumatic fever, a multifactorial, autoimmune, infectious and inflammatory disorder which "licks the joints and bites the heart": A working hypothesis

A novel hypothesis is presented to explain the pathogenesis of the multifactorial autoimmune disorder rheumatic fever (RF). It involves a synergistic interaction among streptococcal toxins, their cell wall components, M protein, immune complexes, complement components, cationic histones. These agents can act with cationic histones released by neutrophils during NETosis and bacteriolysis and can function as opsonic agents possessing properties similar to antibodies. Cationic histones can interact by strong electrostatic forces with negatively- charged domains on immune complexes and complement components. This allows their deposition and endocytosis in the myocardium, the heart valves, and in the joints. However, the main cause of cell and tissue damage observed in RF is due to a synergism among the plethora of pro-inflammatory substances released by activated neutrophils and macrophages. Cell damage may be mitigated to some extent by anionic heparins, heparinoids, and by anti-inflammatory drugs such as corticosteroids which counteract neutrophils and macrophage chemotaxis induced by cytokines.

Comparative Analysis of Fecal Microbiota Composition Between Rheumatoid Arthritis and Osteoarthritis Patients

The aim of this study was to investigate differences between the gut microbiota composition in patients with rheumatoid arthritis (RA) and those with osteoarthritis (OA). Stool samples from nine RA patients and nine OA patients were collected, and DNA was extracted. The gut microbiome was assessed using 16S rRNA gene amplicon sequencing. The structures and differences in the gut microbiome between RA and OA were analyzed. The analysis of diversity revealed no differences in the complexity of samples. The RA group had a lower Bacteroidetes: Firmicutes ratio than did the OA group. Lactobacilli and Prevotella, particularly Prevotella copri, were more abundant in the RA than in the OA group, although these differences were not statistically significant. The relative abundance of Bacteroides and Bifidobacterium was lower in the RA group. At the species level, the abundance of certain bacterial species was significantly lower in the RA group, such as Fusicatenibacter saccharivorans, Dialister invisus, Clostridium leptum, Ruthenibacterium lactatiformans, Anaerotruncus colihominis, Bacteroides faecichinchillae, Harryflintia acetispora, Bacteroides acidifaciens, and Christensenella minuta. The microbial properties of the gut differed between RA and OA patients, and the RA dysbiosis revealed results similar to those of other autoimmune diseases, suggesting that a specific gut microbiota pattern is related to autoimmunity.

Molecular Mimicry, Autoimmunity, and Infection: The Cross-Reactive Antigens of Group A Streptococci and their Sequelae

The group A streptococci are associated with a group of diseases affecting the heart, brain, and joints that are collectively referred to as acute rheumatic fever. The streptococcal immune-mediated sequelae, including acute rheumatic fever, are due to antibody and cellular immune responses that target antigens in the heart and brain as well as the group A streptococcal cross-reactive antigens as reviewed in this article. The pathogenesis of acute rheumatic fever, rheumatic heart disease, Sydenham chorea, and other autoimmune sequelae is related to autoantibodies that are characteristic of autoimmune diseases and result from the immune responses against group A streptococcal infection by the host. The sharing of host and streptococcal epitopes leads to molecular mimicry between the streptococcal and host antigens that are recognized by the autoantibodies during the host response. This article elaborates on the discoveries that led to a better understanding of the pathogenesis of disease and provides an overview of the history and the most current thought about the immune responses against the host and streptococcal cross-reactive antigens in group A streptococcal sequelae.

Applicability of a Modified Rat Model of Acute Arthritis for Long-Term Testing of Drug Delivery Systems

Episodes of inflammation and pain are predominant features of arthritic joint diseases. Drug delivery systems (DDS) could reduce inflammation and pain long-term without chances of infection upon multiple injections. To allow for long-term evaluation of DDS, we modified a previously published acute arthritis model by extending follow-up periods between flare-ups. Unilateral synovial inflammation of the knee was induced by intra-articular injection of streptococcal cell wall peptidoglycan polysaccharide (PGPS), and flare-ups were induced by intravenous PGPS injections every 4 weeks for a total duration of 84 days. In PGPS-reactivated animals, joint swelling, pain behavior, post mortem synovitis, and osteophyte formation were notable features. Hepatitis, splenitis and inflammation of non-primed joints were observed as systemic side effects. To test the applicability of the modified arthritis model for long-term testing of DDS, the duration of anti-inflammatory and analgesic effects of a corticosteroid released from two different polymer-based platforms was evaluated. The current modified arthritis model has good applicability for testing of DDS for a prolonged period of time. Furthermore, the novel autoregulatory polyesteramide (PEA) microsphere platform releasing triamcinolone acetonide (TAA) was benchmarked against poly lactic-co-glycolic acid (PLGA) and reduced joint swelling and pain behavior more potently compared to TAA-loaded PLGA microspheres.

The involvement of Toll-like receptor 9 in the pathogenesis of erosive autoimmune arthritis

Endogenous nucleic acids and their receptors may be involved in the initiation of systemic autoimmune diseases including rheumatoid arthritis (RA). As the role of the DNA sensing Toll-like receptor (TLR) 9 in RA is unclear, we aimed to investigate its involvement in the pathogenesis of autoimmune arthritis using three different experimental models of RA. The data obtained revealed involvement of TLR9 in the T cell-dependent phase of inflammatory arthritis. In rats with pristane-induced arthritis (PIA), TLR9 inhibition before disease onset reduced arthritis significantly and almost completely abolished bone erosion. Accordingly, serum levels of IL-6, α-1-acid-glycoprotein and rheumatoid factor were reduced. Moreover, in TLR9-/- mice, streptococcal cell wall (SCW)-induced arthritis was reduced in the T cell-dependent phase, whereas T cell-independent serum-transfer arthritis was not affected. Remarkably, while TLR7 expression did not change during in vitro osteoclastogenesis, TLR9 expression was higher in precursor cells than in mature osteoclasts and partial inhibition of osteoclastogenesis was achieved only by the TLR9 antagonist. These results demonstrate a pivotal role for TLR9 in the T cell-dependent phases of inflammatory arthritis and additionally suggest some role during osteoclastogenesis. Hence, endogenous DNA seems to be crucially involved in the pathophysiology of inflammatory autoimmune arthritis.

Bacteriolysis - a mere laboratory curiosity?

The role of bacteriolysis in the pathophysiology of microbial infections dates back to 1893 when Buchner and Pfeiffer reported for the first time the lysis of bacteria by immune serum and related this phenomenon to the immune response. Later on, basic anti-microbial peptides and certain beta-lactam antibiotics have been shown not only to kill microorganisms but also to induce bacteriolysis and the release of cell-wall components. In 2009, a novel paradigm was offered suggesting that the main cause of death in sepsis is due to the exclusive release from activated human phagocytic neutrophils (PMNs) traps adhering upon endothelial cells of highly toxic nuclear histone. Since activated PMNs also release a plethora of pro-inflammatory agonists, it stands to reason that these may act in synergy with histone to damage cells. Since certain beta lactam antibiotics may induce bacteriolysis, it is questioned whether these may aggravate sepsis patient's condition. Enigmatically, since the term bacteriolysis and its possible involvement in sepsis is hardly ever mentioned in the extensive clinical articles and reviews dealing with critical care, we hereby aim to refresh the concept of bacteriolysis and its possible role in the pathogenesis of post infectious sequelae.

Experimental animal models for rheumatoid arthritis

Rheumatoid Arthritis (RA) is an autoimmune systemic disorder of unknown etiology and is characterized by chronic inflammation and synovial infiltration of immune cells. RA is associated with decreased life expectancy and quality of life. The research on RA is greatly simplified by animal models that help us to investigate the complex system involving inflammation, immunological tolerance and autoimmunity. The animal models of RA with a proven track record of predictability for efficacy in humans include: collagen type II induced arthritis in rats as well as mice, adjuvant induced arthritis in rats and antigen induced arthritis in several species. The development of novel treatments for RA requires the interplay between clinical observations and studies in animal models. However, each model features a different mechanism driving the disease expression; the benefits of each should be evaluated carefully in making the appropriate choice for the scientific problem to be investigated. In this review article, we focus on animal models of arthritis induced in various species along with the genetic models. The review also discussed the similarity and dissimilarities with respect to human RA.

Contribution of bacterial pathogens to evoking serological disease markers and aggravating disease activity in rheumatoid arthritis

Commensal bacteria and their pathogenic components in the gastrointestinal tract and oral cavity may play pathological roles in autoimmune diseases. To study the possible involvement of bacterial pathogens in autoimmune diseases, IgG and IgA antibodies against pathogenic components produced by three strains of commensal bacteria, Escherichia coli-lipopolysaccharide (E. coli-LPS), Porphyromonas gingivalis-LPS (Pg-LPS) and peptidoglycan polysaccharide (PG-PS) from Streptococcus pyogenes, were determined by an improved ELISA system for sera from two groups of patients with rheumatoid arthritis (RA), who met rapid radiographic progression (RRP) criteria and non-RRP, and compared to normal (NL) controls. Antibody responses to these bacterial pathogens are unique and consistent in individuals, and no fundamental difference was observed between RA and NL controls. Despite the similar antibody responses to pathogens, lower IgG or higher IgA and consequent higher IgA/IgG antibody ratio among the patients with RA related to disease marker levels and disease activity. Peculiarly, the IgA/IgG anti-Pg-LPS antibody ratio resulted from lower IgG and higher IgA antibody responses to Pg-LPS strongly correlated not only with rheumatoid factor (RF), but also correlated with erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and disease activity score of 28 joints with ESR (DAS28-ESR) in the RRP group. In contrast, the IgA/IgG anti-E. coli-LPS and anti-PG-PS antibody ratio correlated or tended to correlate with RF, ESR, CRP, and DAS28-ESR in the non-RRP group, whereas either the IgG or IgA anti-Pg-LPS antibody levels and consequent IgA/IgG anti-Pg-LPS antibody ratio did not correlate with any clinical marker levels in this group. Notably, anti-circular-citrullinated peptide (CCP) antibody levels, which did not correlate with either IgG or IgA antibody levels to any pathogens, did not correlate with severity of arthritis in both RRP and non-RRP. Taken together, we propose that multiple environmental pathogens, which overwhelm the host antibody defense function, contribute independently or concomitantly to evoking disease makers and aggravating disease activity, and affect disease outcomes.

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In Vivo Models for Inflammatory Arthritis

In vivo mouse models of inflammatory arthritis are extensively used to investigate pathogenic mechanisms governing inflammation-driven joint damage. Two commonly utilized models include collagen-induced arthritis (CIA) and methylated bovine serum albumin (mBSA) antigen-induced arthritis (AIA). These offer unique advantages for modeling different aspects of human disease. CIA involves breach of immunological tolerance resulting in systemic autoantibody-driven arthritis, while AIA results in local resolving inflammatory flares and articular T cell-mediated damage. Despite limitations that apply to all animal models of human disease, CIA and AIA have been instrumental in identifying pathogenic mediators, immune cell subsets and stromal cell responses that determine disease onset, progression, and severity. Moreover, these models have enabled investigation of disease phases not easily studied in patients and have served as testing beds for novel biological therapies, including cytokine blockers and small molecule inhibitors of intracellular signaling that have revolutionized rheumatoid arthritis treatment.

Rheumatoid arthritis: identifying and characterising polymorphisms using rat models

Rheumatoid arthritis is a chronic inflammatory joint disorder characterised by erosive inflammation of the articular cartilage and by destruction of the synovial joints. It is regulated by both genetic and environmental factors, and, currently, there is no preventative treatment or cure for this disease. Genome-wide association studies have identified ∼100 new loci associated with rheumatoid arthritis, in addition to the already known locus within the major histocompatibility complex II region. However, together, these loci account for only a modest fraction of the genetic variance associated with this disease and very little is known about the pathogenic roles of most of the risk loci identified. Here, we discuss how rat models of rheumatoid arthritis are being used to detect quantitative trait loci that regulate different arthritic traits by genetic linkage analysis and to positionally clone the underlying causative genes using congenic strains. By isolating specific loci on a fixed genetic background, congenic strains overcome the challenges of genetic heterogeneity and environmental interactions associated with human studies. Most importantly, congenic strains allow functional experimental studies be performed to investigate the pathological consequences of natural genetic polymorphisms, as illustrated by the discovery of several major disease genes that contribute to arthritis in rats. We discuss how these advances have provided new biological insights into arthritis in humans.

The evidence for microbiome manipulation in inflammatory arthritis

The human body consists of millions of commensal bacteria (the microbiome), with the intestinal tract being the most prevalent site of colonization. This colonization process begins at birth, and despite numerous factors such as ageing, diet and drug use affecting the microbiome make-up, by adulthood the composition of the gut bacteria is relatively consistent across local populations. The recent advent of new scientific techniques has enabled us to explore how the microbiome affects health and, in particular, has shed light on the involvement of the microbiome in the pathogenesis of inflammatory disease. In this review we highlight the current evidence for microbiome manipulation in inflammatory arthritis in animal and human models and discuss potential therapeutics targeting the microbiome as treatment for these diseases.

Intestinal Dysbiosis and Rheumatoid Arthritis: A Link between Gut Microbiota and the Pathogenesis of Rheumatoid Arthritis

Characterization and understanding of gut microbiota has recently increased representing a wide research field, especially in autoimmune diseases. Gut microbiota is the major source of microbes which might exert beneficial as well as pathogenic effects on human health. Intestinal microbiome's role as mediator of inflammation has only recently emerged. Microbiota has been observed to differ in subjects with early rheumatoid arthritis compared to controls, and this finding has commanded this study as a possible autoimmune process. Studies with intestinal microbiota have shown that rheumatoid arthritis is characterized by an expansion and/or decrease of bacterial groups as compared to controls. In this review, we present evidence linking intestinal dysbiosis with the autoimmune mechanisms involved in the development of rheumatoid arthritis.

A functional variant of TLR10 modifies the activity of NFkB and may help predict a worse prognosis in patients with rheumatoid arthritis

Background

Toll-like receptor (TLR) family members are key players in inflammation. TLR10 has been poorly studied in chronic inflammatory disorders, and its clinical relevance in rheumatoid arthritis (RA) is as yet unknown. We aimed at identifying TLR10 variants within all coding regions of the gene in patients with RA as well as studying their functional and clinical significance.

Methods

TLR10 gene variants were studied by performing sequencing of 66 patients with RA and 30 control subjects. A selected variant, I473T, was then analyzed in 1654 patients and 1702 healthy control subjects. The capacity of this TLR10 variant to modify the transcriptional activity of nuclear factor kappa-light-chain-enhancer of activated B cells (NFkB) was determined by using a luciferase reporter assay and analyzing the expression of NFkB target genes by quantitative polymerase chain reaction. Differences between groups were analyzed by using the Mann-Whitney U test and the unpaired two-tailed Student’s t test.

Results

We detected ten missense variants in the TLR10 gene and focused on the I473T substitution based on allele frequencies and the predicted functional impact. I473T variant is not associated with susceptibility to RA, but it significantly correlates with erosive disease in patients seropositive for antibodies to citrullinated protein antigens (p = 0.017 in the total cohort and p = 0.0049 in female patients) and with a lower response to infliximab treatment as measured by the change in Disease Activity Score in 28 joints (p = 0.012) and by the European League Against Rheumatism criteria (p = 0.049). Functional studies showed that TLR10 reduced activation of the NFkB inflammatory pathway in hematopoietic cells, whereas the I473T variant lacked this inhibitory capacity. Consistently, after exposure to infliximab, cells expressing the I437T variant showed higher NFkB activity than cells carrying wild-type TLR10.

Conclusions

A TLR10 allelic variant, I473T, has impaired NFkB inhibitory activity and is highly associated with disease severity and low response to infliximab in patients with RA.

Treating experimental arthritis with the innate immune inhibitor interleukin-37 reduces joint and systemic inflammation

OBJECTIVES

The IL-1 family member IL-37 was recently characterized as a fundamental inhibitor of innate inflammation. We investigated the effects of recombinant IL-37 in joint inflammation and joint pathology in a mouse model of arthritis. In addition, we explored the potential for therapeutic use in human joint inflammation.

METHODS

Wild-type mice were treated systemically with a recombinant form of the naturally occurring human IL-37, and then the knee joints were injected with streptococcal cell wall fragments; joint inflammation, synovial cytokine concentrations and histology were evaluated after 24 h. Mice deficient in the IL-1 family decoy receptor IL-1R8 were treated in a similar manner. The effects of IL-37 treatment were also assessed in a model of streptococcal cell wall-induced systemic inflammation. Changes in IL37 and IL1R8 gene expression were evaluated in the synovia of patients with rheumatoid arthritis.

RESULTS

In wild-type mice, low doses (40 µg/kg) of IL-37 suppressed joint inflammation by 51.7% (P < 0.001) and significantly decreased synovial IL-1β by 84%, IL-6 by 73%, TNF-α by 33%, chemokine (C-X-C motif) ligand 1 by 58%, Chemokine (C-C motif) ligand 3 or macrophage inflammatory protein 1-alpha by 64%, IL-1α by 40% and MPO by 60%. These reductions were associated with a lower recruitment of neutrophils into the joint. The anti-inflammatory properties of IL-37 were dependent on the presence of IL-1R8, also in streptococcal cell wall-induced peritonitis. We found that gene expression of IL1R8, but not IL37, is markedly increased in the synovia of patients with rheumatoid arthritis.

CONCLUSION

IL-37 emerges as a key suppressor of joint and systemic inflammation. These findings indicate a rationale for using recombinant IL-37 in the treatment of arthritis.

Animal Models of Bone Loss in Inflammatory Arthritis: from Cytokines in the Bench to Novel Treatments for Bone Loss in the Bedside-a Comprehensive Review

Throughout life, bone is continuously remodelled. Bone is formed by osteoblasts, from mesenchymal origin, while osteoclasts induce bone resorption. This process is tightly regulated. During inflammation, several growth factors and cytokines are increased inducing osteoclast differentiation and activation, and chronic inflammation is a condition that initiates systemic bone loss. Rheumatoid arthritis (RA) is a chronic inflammatory auto-immune disease that is characterised by active synovitis and is associated with early peri-articular bone loss. Peri-articular bone loss precedes focal bone erosions, which may progress to bone destruction and disability. The incidence of generalised osteoporosis is associated with the severity of arthritis in RA and increased osteoporotic vertebral and hip fracture risk. In this review, we will give an overview of different animal models of inflammatory arthritis related to RA with focus on bone erosion and involvement of pro-inflammatory cytokines. In addition, a humanised endochondral ossification model will be discussed, which can be used in a translational approach to answer osteoimmunological questions.

Anti-Inflammatory Effects of the Essential Oils of Ginger (Zingiber officinale Roscoe) in Experimental Rheumatoid Arthritis

Ginger and its extracts have been used traditionally as anti-inflammatory remedies, with a particular focus on the medicinal properties of its phenolic secondary metabolites, the gingerols. Consistent with these uses, potent anti-arthritic effects of gingerol-containing extracts were previously demonstrated by our laboratory using an experimental model of rheumatoid arthritis, streptococcal cell wall (SCW)-induced arthritis. In this study, anti-inflammatory effects of ginger's other secondary metabolites, the essential oils (GEO), which contain terpenes with reported phytoestrogenic activity, were assessed in female Lewis rats with SCW-induced arthritis. GEO (28 mg/kg/d ip) prevented chronic joint inflammation, but altered neither the initial acute phase of joint swelling nor granuloma formation at sites of SCW deposition in liver. Pharmacologic doses of 17-β estradiol (200 or 600 μg/kg/d sc) elicited the same pattern of anti-inflammatory activity, suggesting that GEO could be acting as a phytoestrogen. However, contrary to this hypothesis, GEO had no in vivo effect on classic estrogen target organs, such as uterus or bone. En toto, these results suggest that ginger's anti-inflammatory properties are not limited to the frequently studied phenolics, but may be attributable to the combined effects of both secondary metabolites, the pungent-tasting gingerols and as well as its aromatic essential oils.

Methods for Testing Immunological Factors

Hypersensitivity reactions can be elicited by various factors: either immunologically induced, i.e., allergic reactions to natural or synthetic compounds mediated by IgE, or non-immunologically induced, i.e., activation of mediator release from cells through direct contact, without the induction of, or the mediation through immune responses. Mediators responsible for hypersensitivity reactions are released from mast cells. An important preformed mediator of allergic reactions found in these cells is histamine. Specific allergens or the calcium ionophore 48/80 induce release of histamine from mast cells. The histamine concentration can be determined with the o-phthalaldehyde reaction.

Does the buck stop with the bugs?: an overview of microbial dysbiosis in rheumatoid arthritis

The human body is an environmental niche which is home to diverse co-habiting microbes collectively referred as the human microbiome. Recent years have seen the in-depth characterization of the human microbiome and associations with diseases. Linking of the composition or number of the human microbiota with diseases and traits date back to the original work of Elie Metchnikoff. Recent advances in genomic technologies have opened up finer details and dynamics of this new science with higher precision. Microbe-rheumatoid arthritis connection, largely related to the gut and oral microbiomes, has showed up as a result - apart from several other earlier, well-studied candidate autoimmune diseases. Although evidence favouring roles of specific microbial species, including Porphyromonas, Prevotella and Leptotricha, has become clearer, mechanistic insights still continue to be enigmatic. Manipulating the microbes by traditional dietary modifications, probiotics, and antibiotics and by currently employed disease-modifying agents seems to modulate the disease process and its progression. In the present review, we appraise the existing information as well as the gaps in knowledge in this challenging field. We also discuss the future directions for potential clinical applications, including prevention and management of rheumatoid arthritis using microbial modifications.

Rheumatoid arthritis vaccine therapies: perspectives and lessons from therapeutic ligand epitope antigen presentation system vaccines for models of rheumatoid arthritis

The current status of therapeutic vaccines for autoimmune diseases is reviewed with rheumatoid arthritis as the focus. Therapeutic vaccines for autoimmune diseases must regulate or subdue responses to common self-antigens. Ideally, such a vaccine would initiate an antigen-specific modulation of the T-cell immune response that drives the inflammatory disease. Appropriate animal models and types of T helper cells and signature cytokine responses that drive autoimmune disease are also discussed. Interpretation of these animal models must be done cautiously because the means of initiation, autoantigens, and even the signature cytokine and T helper cell (Th1 or Th17) responses that are involved in the disease may differ significantly from those in humans. We describe ligand epitope antigen presentation system vaccine modulation of T-cell autoimmune responses as a strategy for the design of therapeutic vaccines for rheumatoid arthritis, which may also be effective in other autoimmune conditions.

Fecal Microbiota Transplantation: A Review of Emerging Indications Beyond Relapsing Clostridium difficile Toxin Colitis

The symbiotic relationship between gut microbiota and humans has been forged over many millennia. This relationship has evolved to establish an intimate partnership that we are only beginning to understand. Gut microbiota were once considered pathogenic, but the concept of gut microbiota and their influence in human health is undergoing a major paradigm shift, as there is mounting evidence of their impact in the homeostasis of intestinal development, metabolic activities, and the immune system. The disruption of microbiota has been associated with many gastrointestinal and nongastrointestinal diseases, and the reconstitution of balanced microbiota has been postulated as a potential therapeutic strategy. Fecal microbiota transplantation (FMT), a unique method to reestablish a sustained balance in the disrupted microbiota of diseased intestine, has demonstrated great success in the treatment of recurrent Clostridium difficile infection and has gained increasing acceptance in clinical use. The possibility of dysfunctional micro-biota playing a causative role in other gastrointestinal and nongas-trointestinal diseases, therefore, has also been raised, and there are an increasing number of studies supporting this hypothesis. FMT is emerging as a feasible therapeutic option for several diseases; however, its efficacy remains in question, given the lack of clinical trial data. Altering microbiota with FMT holds great promise, but much research is needed to further define FMT's therapeutic role and optimize the microbiota delivery system.

Etanercept ameliorates inflammation and pain in a novel mono-arthritic multi-flare model of streptococcal cell wall induced arthritis

Background

The impact of anti-TNF, corticosteroid and analgesic therapy on inflammation and pain was evaluated in a novel mono-arthritic multi-flare rat Streptococcal Cell Wall (SCW) model using Etanercept, Dexamethasone and Buprenorphine.

Methods

Multiple flares of arthritis were induced with an intra-articular injection of SCW in the hind ankle on day 1, followed by intravenous challenges on days 21 and 42. Inflammation and pain were monitored in the hind paws. Cytokine profiling, cell phenotyping, bioluminescence imaging and histopathological evaluation were also performed.

Results

Local injection of SCW caused a rapid onset of inflammation and pain in the injected ankle which resolved within 4 days (Flare 1). Intravenous injection 20 days after sensitization resulted in an increase in ankle diameter and pain, which partially resolved in 8 days (Flare 2). The subsequent intra-venous injection in the same animals 14 days after resulted in a more chronic disease with inflammation and pain persisting over a period of 10 days (Flare 3). In Flare 2, therapeutic administration of Dexamethasone inhibited paw swelling (95%; P<0.001) and pain (55%; P<0.05). Therapeutic administration of Buprenorphine inhibited pain (80%; P<0.001) without affecting paw swelling (0%). Prophylactic administration of Etanercept in Flare 2 inhibited paw swelling (≥60%; P<0.001) and pain by ≥30%. Expression of IL-1β, IL-6, MCP-1 and CINC was reduced by >50% (P<0.001). Treatment with Etanercept in Flare 3 inhibited paw swelling by 60% (P<0.001) and pain by 25%. Prior treatment with Etanercept in Flare 2 followed by re-administration in Flare 3 led to a complete loss in the efficacy of Etanercept. Systemic exposure of Etanercept corroborated with lack of efficacy. Dexamethasone inhibited inflammation and pain in both Flares 2 and 3 (P<0.001).

Conclusions

We established a novel multi-flare SCW arthritis model enabling drug intervention in different stages of disease. We show for the first time the evaluation of inflammation and pain simultaneously in this model. Etanercept and Dexamethasone inhibited inflammation, pain and proinflammatory cytokines in this model. Taken together, this model facilitates the assessment of anti-rheumatic agents targeting inflammation and pain in the multiple flare paradigm and offers a powerful tool for drug discovery.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-409) contains supplementary material, which is available to authorized users.

Modeling pharmacokinetics/pharmacodynamics of abatacept and disease progression in collagen-induced arthritic rats: a population approach

The PK/PD of abatacept, a selective T cell co-stimulation modulator, was examined in rats with collagen-induced arthritis (CIA) using a nonlinear mixed effect modeling approach. Male Lewis rats underwent collagen induction to produce rheumatoid arthritis. Two single-dose groups received either 10 mg/kg intravenous (IV) or 20 mg/kg subcutaneous (SC) abatacept, and one multiple-dose group received one 20 mg/kg SC abatacept dose and four additional 10 mg/kg SC doses. Effects on disease progression (DIS) were measured by paw swelling. Plasma concentrations of abatacept were assayed by enzyme-linked immunosorbent assay. The PK/PD data were sequentially fitted using NONMEM VI. Goodness-of-fit was assessed by objective functions and visual inspection of diagnostic plots. The PK of abatacept followed a two-compartment model with linear elimination. For SC doses, short-term zero-order absorption was assumed with F = 59.2 %. The disease progression component was an indirect response model with a time-dependent change in paw edema production rate constant (k in ) that was inhibited by abatacept. Variation in the PK data could be explained by inter-individual variability in clearance and central compartment volume (V 1 ), while the large variability of the PD data may be the result of paw edema production (k in 0 ) and loss rate constant (k out ). Abatacept has modest effects on paw swelling in CIA rats. The PK/PD profiles were well described by the proposed model and allowed evaluation of inter-individual variability on drug- and DIS-related parameters.

Hepcidin antagonists for potential treatments of disorders with hepcidin excess

The discovery of hepcidin clarified the basic mechanism of the control of systemic iron homeostasis. Hepcidin is mainly produced by the liver as a propeptide and processed by furin into the mature active peptide. Hepcidin binds ferroportin, the only cellular iron exporter, causing the internalization and degradation of both. Thus hepcidin blocks iron export from the key cells for dietary iron absorption (enterocytes), recycling of hemoglobin iron (the macrophages) and the release of storage iron from hepatocytes, resulting in the reduction of systemic iron availability. The BMP/HJV/SMAD pathway is the major regulator of hepcidin expression that responds to iron status. Also inflammation stimulates hepcidin via the IL6/STAT3 pathway with a support of an active BMP/HJV/SMAD pathway. In some pathological conditions hepcidin level is inadequately elevated and reduces iron availability in the body, resulting in anemia. These conditions occur in the genetic iron refractory iron deficiency anemia and the common anemia of chronic disease (ACD) or anemia of inflammation. Currently, there is no definite treatment for ACD. Erythropoiesis-stimulating agents and intravenous iron have been proposed in some cases but they are scarcely effective and may have adverse effects. Alternative approaches aimed to a pharmacological control of hepcidin expression have been attempted, targeting different regulatory steps. They include hepcidin sequestering agents (antibodies, anticalins, and aptamers), inhibitors of BMP/SMAD or of IL6/STAT3 pathway or of hepcidin transduction (siRNA/shRNA) or ferroportin stabilizers. In this review we summarized the biochemical interactions of the proteins involved in the BMP/HJV/SMAD pathway and its natural inhibitors, the murine and rat models with high hepcidin levels currently available and finally the progresses in the development of hepcidin antagonists, with particular attention to the role of heparins and heparin sulfate proteoglycans in hepcidin expression and modulation of the BMP6/SMAD pathway.

Endothelial dysfunction in an ovine model of collagen-induced arthritis

BACKGROUND

Rheumatoid arthritis (RA) induces systemic inflammation, producing a range of co-morbidities including cardiovascular disease. An early vascular change is endothelial dysfunction, characterized by reduced endothelium-dependent vasodilation. The aim of this study was to assess endothelial function in isolated coronary and digital arteries using an ovine model of collagen-induced RA.

METHODS

Sheep were culled following induction of arthritis, and their endothelial function was compared to that of normal sheep. Paired arterial segments were mounted in a wire myograph and dilated with endothelium-dependent vasodilators [bradykinin, serotonin, carbachol and adenosine diphosphate (ADP); linked to either Gi or Gq signalling pathways] and endothelium-independent dilators (adenosine and sodium nitroprusside) to construct cumulative concentration-response curves.

RESULTS

Coronary arteries from arthritic sheep exhibited a significantly greater EC50 value for bradykinin-induced relaxation compared to non-arthritic controls (2.9 × 10(-8) M for arthritic sheep vs. 8.6 × 10(-9) M for controls). Digital arteries from arthritic sheep also exhibited a significantly greater EC50 for relaxation to ADP and a significant decrease in the carbachol maximal response. Responses to sodium nitroprusside were unchanged in both coronary and digital arteries.

CONCLUSION

Sheep with RA demonstrated attenuated arterial relaxation to endothelium-dependent vasodilators. This may provide a useful model of endothelial dysfunction in chronic inflammatory conditions. The dysfunction did not appear to be associated with one specific G-protein signalling pathway.

Upregulation of TLR2 expression is induced by estrogen via an estrogen-response element (ERE)

TLR2 and estrogen are both thought to be involved in the pathogenesis of RA; however, it is unknown if there is an association between estrogen and TLR2. In this report, we treated PMA-differentiated THP-1 cells with 17β-estradiol (E2) and observed increases in TLR2 mRNA and protein levels by real-time quantitative PCR and western blot. Transfection of THP-1 cells with a series of 5'-deleted TLR2 promoter-luciferase constructs revealed that E2 enhanced TLR2 transcriptional activity in an estrogen receptor alpha (ERα)-dependent pattern. An estrogen receptor response element (ERE) was identified 251 bases upstream of the TLR2 promoter, and electrophoretic mobility shift assay and chromatin immunoprecipitations showed ERα binding was increased by E2. In summary, this work demonstrated that TLR2 is a new estrogen-regulated gene whose expression is upregulated through the interaction of ERα with an ERE in the promoter region.

Enhancement of kinase selectivity in a potent class of arylamide FMS inhibitors

Structure-activity relationship (SAR) studies on a highly potent series of arylamide FMS inhibitors were carried out with the aim of improving FMS kinase selectivity, particularly over KIT. Potent compound 17r (FMS IC50 0.7 nM, FMS cell IC50 6.1 nM) was discovered that had good PK properties and a greater than fivefold improvement in selectivity for FMS over KIT kinase in a cellular assay relative to the previously reported clinical candidate 4. This improved selectivity was manifested in vivo by no observed decrease in circulating reticulocytes, a measure of bone safety, at the highest studied dose. Compound 17r was highly active in a mouse pharmacodynamic model and demonstrated disease-modifying effects in a dose-dependent manner in a strep cell wall-induced arthritis model of rheumatoid arthritis in rats.

Toll-like receptor polymorphisms and rheumatoid arthritis: a systematic review

The aim of this study was to determine whether toll-like receptor (TLR) polymorphisms confer susceptibility to rheumatoid arthritis (RA) and influence the clinical characteristics of RA. The authors conducted a systematic review on associations between TLR polymorphisms and RA susceptibility and clinical findings. Meta-analysis was performed if at least three comparisons of an issue were available. A total of 14 studies were included in this systematic review, which included European and Asian studies. Meta-analysis of five European studies showed no association between the TLR4 Asp299Gly (rs4986790) polymorphism and RA (OR for the minor allele = 0.907, 95% CI = 0.755-1.088, p = 0.291). Furthermore, none of these studies found any association between the polymorphism and clinical characteristics. A significant difference between TLR9 rs187084 allele frequencies in RA patients and controls was found in one Turkish study (p = 0.003), and a moderate association between RF positivity and TLR8 rs5741883 was found in an European study (p = 0.001). The numbers of guanine-thymine [(GT)n] repeats in intron II of the TLR2 gene were found a significantly higher S-allele frequency in Korean patients with RA than in controls (30.3 vs. 23.0 %, p = 0.03). This meta-analysis shows lack of an association between the TLR4 Asp299Gly polymorphism and RA. However, our finding suggests the possibility that TLR polymorphisms are associated with the development and clinical characteristics of RA. Because of a paucity of data of the TLR polymorphisms, case-control studies are required to determine whether TLR2, 4, 8, 9 polymorphisms contribute to RA susceptibility or severity in more than 2,000 patients and controls.

The spectrum of group A streptococcal joint pathology in the acute care setting

OBJECTIVES

Group A streptococcus (GAS) is a frequent cause of pediatric musculoskeletal infections including septic arthritis, acute rheumatic fever (ARF), and a more benign arthritis called post-streptococcal reactive arthritis. Children with painful joints are frequently evaluated in the acute care setting, and because the presentation of each of these entities is similar, the diagnosis can be difficult to make. Five cases of children with GAS arthridities are presented to demonstrate the spectrum of GAS-associated joint pathologies encountered in the acute care setting and also to discuss how GAS laboratory tests may assist in the evaluation and management of children presenting with a painful joint.

METHODS

Five cases of GAS-associated joint pathology are presented. Evaluation of these patients was conducted using a diagnostic algorithm derived from a literature review of post-streptococcal reactive arthritis and ARF, as well as the current clinical practice guideline for the diagnosis and treatment of septic arthritis.

RESULTS

The 5 cases presented include 1 case of transient synovitis, 2 cases of inflammatory synovitis, 1 case of septic arthritis, and 1 case of ARF.

CONCLUSIONS

Determining the cause of joint pain in the acute care setting is challenging. The addition of the GAS laboratory tests to a diagnostic algorithm based on clinical examination and monitoring systemic inflammation can help to identify patients with ARF and septic arthritis in the acute care setting. In addition, GAS-specific laboratory tests may help to identify cases of nonseptic, non-ARF GAS joint pathology.

Treatment of erythropoietin deficiency in mice with systemically administered siRNA

Anemia linked to a relative deficiency of renal erythropoietin production is a significant cause of morbidity and medical expenditures in the developed world. Recombinant erythropoietin is expensive and has been linked to excess cardiovascular events. Moreover, some patients become refractory to erythropoietin because of increased production of factors such as hepcidin. During fetal life, the liver, rather than the kidney, is the major source of erythropoietin. In the present study, we show that it is feasible to reactivate hepatic erythropoietin production and suppress hepcidin levels using systemically delivered siRNAs targeting the EglN prolyl hydroxylases specifically in the liver, leading to improved RBC production in models of anemia caused by either renal insufficiency or chronic inflammation with enhanced hepcidin production.

Destructive role of myeloid differentiation factor 88 and protective role of TRIF in interleukin-17-dependent arthritis in mice

OBJECTIVE

Increasing evidence indicates the involvement of Toll-like receptors (TLRs) in the progression of arthritis; however, the contribution of the two signaling pathways used by TLRs, which are mediated by myeloid differentiation factor 88 (MyD88) and TRIF, remains unclear. The objective of this study was to investigate the specific roles of MyD88 and TRIF in chronic experimental arthritis and the accompanying adaptive immune responses.

METHODS

Chronic arthritis was induced in wild-type, MyD88(-/-) , and Trif(lps2) (TRIF(-/-) ) mice by repetitive intraarticular injections of streptococcal cell wall (SCW) fragments. SCW-specific T cell and B cell responses, joint swelling, and histopathologic changes were analyzed during chronic arthritis.

RESULTS

Both MyD88 and TRIF pathways contributed to antigen-specific T cell proliferation and antibody production, with the MyD88 pathway playing the dominant role. The severity of joint swelling and synovial inflammation, as well as the histopathologic damage to cartilage and bone, was strongly dependent on MyD88 signaling, whereas TRIF was redundant. MyD88 signaling was critical for the development of pathogenic T cell response (i.e., interleukin-17 [IL-17] production) in response to SCW antigen. Interestingly, when the T cell-dependent phase was prolonged, TRIF signaling appeared to down-regulate bone erosion, an effect accompanied by an inhibitory effect on IL-17 production.

CONCLUSION

This study reveals a central role of MyD88 and a counterregulatory function of TRIF in T cell-driven arthritis. The findings provide a rationale for a pathway-specific interference in order to block the pathogenic features and to preserve or stimulate the beneficial aspects of TLR signaling.

Toll-like receptor--a potent driving force behind rheumatoid arthritis

Toll like receptor (TLR), one of the key functions of innate immune system, can recognize not only exogenous pathogen-associated molecular patterns, namely PAMPs, but also endogenous molecules created upon tissue injury, sterile inflammation and degeneration. Endogenous TLR ligands are called as damage-associated molecular patters (DAMPs), including endogenous molecules released by activated and necrotic cells, and extracellular matrix molecules. DAMPs are also known as alarmins. TLR research has brought about new insights in the rheumatic diseases. Previous reports suggest that TLRs and the signal pathways intensively contribute to the pathogenesis of rheumatoid arthritis (RA) and other arthritic conditions with interaction of various TLR ligands. Accumulated knowledge of TLR system is summarized to overlook TLRs and the signaling pathway in arthritis conditions, with special reference to RA.

Suppression of collagen-induced arthritis by intra-articular lentiviral vector-mediated delivery of Toll-like receptor 7 short hairpin RNA gene

Knockdown of Toll-like receptors (TLRs) is a novel therapeutic strategy in treating patients with rheumatoid arthritis (RA). We examined the effects of lentiviral vector-mediated delivery of TLR7 short hairpin RNA gene (Lt.shTLR7) on collagen-induced arthritis (CIA). After being immunized on days 0 and 7, Sprague-Dawley rats received intra-articular (i.a.) injection of Lt.shTLR7 or scramble control vector on days 7 and 10. The therapeutic effects were evaluated by measuring ankle circumferences, articular index, and radiographic and histological scores on killing on day 16. Microvessel densities, vascular endothelial growth factor (VEGF) levels, pro-inflammatory cytokine concentrations and T-cell numbers within the synovial tissues were measured. Moreover, VEGF and pro-inflammatory cytokine concentrations in culture supernatants from TLR7-transfected synovial fibroblasts (SFs) stimulated with imiquimod or endogenous ligands were examined. There were significant reduction in ankle circumferences, articular indexes, and radiographic and histological scores. Microvessel densities, VEGF concentrations, interleukin (IL)-1β and IL-6 levels and T-cell densities within synovial tissues were significantly lower. Induction of VEGF, IL-1β and IL-6 production from stimulated SFs was significantly suppressed. Taken together, these data demonstrate the effects of i.a. lentiviral vector-mediated delivery of shTLR7 RNA gene on inhibition of CIA, and implicate the manipulation of TLR7 as a potential therapeutic strategy in RA patients.

Clopidogrel, a P2Y12 receptor antagonist, potentiates the inflammatory response in a rat model of peptidoglycan polysaccharide-induced arthritis

The P2Y12 receptor plays a crucial role in the regulation of platelet activation by several agonists, which is irreversibly antagonized by the active metabolite of clopidogrel, a widely used anti-thrombotic drug. In this study, we investigated whether reduction of platelet reactivity leads to reduced inflammatory responses using a rat model of erosive arthritis. We evaluated the effect of clopidogrel on inflammation in Lewis rats in a peptidoglycan polysaccharide (PG-PS)-induced arthritis model with four groups of rats: 1) untreated, 2) clopidogrel-treated, 3) PG-PS-induced, and 4) PG-PS-induced and clopidogrel-treated. There were significant differences between the PG-PS+clopidogrel group when compared to the PG-PS group including: increased joint diameter and clinical manifestations of inflammation, elevated plasma levels of pro-inflammatory cytokines (IL-1 beta, interferon (IFN) gamma, and IL-6), an elevated neutrophil blood count and an increased circulating platelet count. Plasma levels of IL-10 were significantly lower in the PG-PS+clopidogrel group compared to the PG-PS group. Plasma levels of platelet factor 4 (PF4) were elevated in both the PG-PS and the PG-PS+clopidogrel groups, however PF4 levels showed no difference upon clopidogrel treatment, suggesting that the pro- inflammatory effect of clopidogrel may be due to its action on cells other than platelets. Histology indicated an increase in leukocyte infiltration at the inflammatory area of the joint, increased pannus formation, blood vessel proliferation, subsynovial fibrosis and cartilage erosion upon treatment with clopidogrel in PG-PS-induced arthritis animals. In summary, animals treated with clopidogrel showed a pro-inflammatory effect in the PG-PS-induced arthritis animal model, which might not be mediated by platelets. Elucidation of the mechanism of clopidogrel-induced cell responses is important to understand the role of the P2Y12 receptor in inflammation.

Intrinsic danger: activation of Toll-like receptors in rheumatoid arthritis

RA is a debilitating disorder that manifests as chronic localized synovial and systemic inflammation leading to progressive joint destruction. Recent advances in the molecular basis of RA highlight the role of both the innate and adaptive immune system in disease pathogenesis. Specifically, data obtained from in vivo animal models and ex vivo human tissue explants models has confirmed the central role of Toll-like receptors (TLRs) in RA. TLRs are pattern recognition receptors (PRRs) that constitute one of the primary host defence mechanisms against infectious and non-infectious insult. This receptor family is activated by pathogen-associated molecular patterns (PAMPs) and by damage-associated molecular patterns (DAMPs). DAMPs are host-encoded proteins released during tissue injury and cell death that activate TLRs during sterile inflammation. DAMPs are also proposed to drive aberrant stimulation of TLRs in the RA joint resulting in increased expression of cytokines, chemokines and proteases, perpetuating a vicious inflammatory cycle that constitutes the hallmark chronic inflammation of RA. In this review, we discuss the signalling mechanisms of TLRs, the central function of TLRs in the pathogenesis of RA, the role of endogenous danger signals in driving TLR activation within the context of RA and the current preclinical and clinical strategies available to date in therapeutic targeting of TLRs in RA.